Probing the Microscopic Behavior of PFOS Clustering and Adsorption at LNAPL Interfaces; a PFOS-Water-Cyclohexane...

Area of Science:

• Environmental Chemistry
• Environmental Science
• Physical Chemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants.
• Perfluorooctanesulfonic acid (PFOS) is prevalent in firefighting foams and often co-occurs with petroleum hydrocarbons (LNAPL) in soil and groundwater.
• PFOS partitioning at LNAPL-water interfaces is complex and difficult to study with traditional methods.

Purpose of the Study:

• To investigate the behavior of supersaturated PFOS at LNAPL-water interfaces using molecular dynamics simulations.
• To understand PFOS micellization and partitioning dynamics.
• To assess the influence of counterions on PFOS adsorption and micellization.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model supersaturated PFOS.
• Simulations focused on the behavior of PFOS at the interface between LNAPL and water.
• The effect of sodium and hydronium counterions on PFOS partitioning was investigated.

Main Results:

• Significant adsorption of PFOS was observed at LNAPL-water interfaces.
• These interfaces act as substantial retention sites and potential long-term sources of PFOS contamination.
• PFOS adsorption and micellization are significantly influenced by the presence of sodium and hydronium ions.

Conclusions:

• LNAPL-water interfaces are critical sites for PFOS retention and release.
• Water chemistry, specifically counterion type, plays a crucial role in PFOS partitioning behavior.
• Understanding these interactions may offer pathways for managing PFOS contamination.